1. Field of the Invention
The present invention relates to a milling machine that is NC controlled and methods of milling and menu selection.
2. Description of the Related Art
FIG. 20 shows an object 11A which were mounted on a X-Y stage 10. Assume X-Y-Z rectangular coordinate system as illustrated.
A portion of a intersection line 13 of a plane 12 of Z being constant and an object 11A is formed by moving an end mill along the path, shown in FIG. 21, in order from outside to inside to cut a rectangular block material 14.
Reference character 11 is the design plane to form the object 11A. FIG. 22(A) shows the state that the material 14 is being cut with an end mill 16 along a path element L1 which is equal to the boundary of material 14. When going around on the path element L1 once, the end mill 16 is shifted into the inside path element. Similar processing is repeated. To cut near the intersection line 13 along a inside path element L2, the end mill 16 is turned around. Therefore, after the switchback, end mill 16 becomes the state shown in FIG. 22(B). The load of end mill 16 increases more than the case of FIG. 22(A).
Since there is not wastefulness in the conventional end mill path, it is efficient apparently. However, since the load of end mill 16 increases rapidly with the switchback path, end mill 16 becomes easy to damage, resulting in a short lifetime. Therefore, when manufacturing without an operator at night and end mill 16 being damaged, work would be stopped and the work efficiency becomes bad as a result.
By the way, when milling an indented surface of a work with a ball end mill, the larger the diameter of the ball end mill, the better efficiency is achieved in milling. This diameter is limited by the curvature of the indented surface. In the prior art, the operator takes into consideration the approximate contour of the indented surface of the work and, allowance for a margin, selects a ball end mill with a somewhat smaller diameter, resulting in a poor milling efficiency.
In addition, when performing slight offset milling over the entire surface after milling is performed in conformance to the design, a new design surface must be input to the computer to calculate the path of the ball end mill for the new design surface, causing the processing to become complicated.
Also, when issuing a milling command to the computer that controls the milling machine, a menu is displayed to select items in each hierarchical layer through the top down method. Therefore, the number of selections that must be made is large, resulting in poor operability and difficulty for the operator in grasping the overall menu structure.